There is a well recognized need for devices that enable a single individual to transport heavy and awkward panel shaped objects such as plywood sheets, gypsum board, tables, doors and similarly shaped objects. This is evident by a number of patented devices for this purpose and several commercially available products.
Many different methods and apparatus are available for this type of transport. Some methods involve placing the panel onto four wheel carts or dollies. Others use two wheel hand trucks which support a panel from the side. Another approach is to use a two wheel dolly which supports the panel by an edge with wheels placed parallel to the panel face on opposite sides of the panel.
Two wheel dollies provide advantages compared to four wheel carts, four wheel dollies and two wheel hand trucks. The smaller size and configuration of a wheel placed on each side of the dolly provides stable support while enabling panels to be maneuvered through narrow openings.
Despite advantages that two wheel panel dollies have over four wheel carts, four wheel dollies and hand trucks, the existing two wheel dolly designs also have several disadvantages which have prevented widespread adoption. Two key challenges are to provide a suitable method to secure a panel to a dolly and a method to hold a dolly in place while a panel is loaded onto it.
Patents of prior art document several methods to secure a panel to a two wheel dolly such as resting the panel on a high friction surface, V or U grooves, a vertical support, clamping bars and screw clamps applied to the sides of the panel.
Several other methods have been used to hold the dolly in place while a panel is set onto it such as stabilizing legs, long arms and locking levers.
The following patents reflect prior art and methods for securing panels to two wheeled dollies:
U.S. Pat. No. 3,845,969Nov. 5, 1974NadeauU.S. Pat. No. 4,270,741Jun. 1, 1981HurstU.S. Pat. No. 5,284,410Feb. 8, 1994SpectorU.S. Pat. No. 4,695,067Sep. 22, 1987WilleyU.S. Pat. No. 5,820,145Oct. 13, 1998OsowskiU.S. Pat. No. 5,988,659Nov. 13, 1999YoungU.S. Pat. No. 6,234,499May 22, 2001IrwinU.S. Pat. No. 6,250,655Jun. 6, 2001SheeksU.S. Pat. No. 6,663,123Dec. 16, 2003KovacsU.S. Pat. No. 6,886,274Mar. 15, 2005MuscatU.S. Pat. No. 7,896,367Mar. 1, 2011SupronoU.S. Pat. No. 8,002,510Aug. 23, 2011WilliamsU.S. Pat. No. 6,308,969Oct. 30, 2011YoungU.S. Pat. No. 8,100,419Jan. 24, 2012Morisset
One disadvantage of current techniques and designs is that placing a panel onto the dolly requires a user to pick up a heavy and awkward panel, and then accurately place the panel edge into a narrow slot or opening that is itself on a rolling platform. This task eliminates much of the advantage of using a two wheel dolly since manual lifting and maneuvering, which is difficult for a single user, must still be done and may require help from a second person.
Another disadvantage of current two wheel dollies is the methods for balancing and securing the load over the wheels. A panel that is not securely attached can bounce and slip during movement. During transport a panel may need to be lifted over an obstacle such as a curb or stairs. If not firmly attached, or without constant action from the user, the panel and dolly will be separated and must then be reattached after moving both over the obstacle. Methods that rely on the weight of the object to provide clamping force are not effective for this purpose since lifting the object will remove the clamping force.
The width of panels expected to be transported by a single user typically range from a quarter inch for a sheet of plywood to three inches for a door or window frame. Current designs for clamps that apply pressure to the panel sides cannot accommodate this range of widths, or require additional adjustments and time spent by the user.
Some patented two wheel dollies provide clamping mechanisms to secure the panel to the dolly which significantly increases the size and weight of the dolly that must be carried with the panel or removed if it is lifted over an obstacle. Other clamping mechanisms involve long arms or bars which make the two wheel dolly awkward to store and transport.
Clamping mechanisms with a long bar arranged vertically to provide a sliding clamp from the top cannot clamp more than one panel at a time if the panels have different heights. For example, if a forty eight inch wide sheet of plywood is carried with a thirty six inch wide sheet of plywood, only the larger panel can be clamped.